The accumulation of water within the walls of building structures may cause the building structure to prematurely deteriorate. Water may penetrate through the exterior building material causing the building materials to, for example, mold, mildew or rot. In addition, the walls of a building structure are particularly susceptible to water invasion where they interface with, for example, windows, doors, cracks, adjacent roofs or electrical boxes. Therefore, the moisture needs a way to escape or evaporate before penetrating the material of the inner wall of a building structure.
In order to prevent the accumulation of water or moisture, many materials have been used to separate an inner sheathing material from an outer building cladding of a building structure. For example, corrugated foam has been used as a separator by attaching it to the inner sheathing material with an adhesive. However, this process does not provide a path for the moisture to escape. For example, the adhesive or glue during installation causes the grooves to become clogged, thus, blocking the water's path to escape through the grooves. In addition, because the foam is installed in vertical tiers on the inner sheathing material, the grooves from an upper tier may not be aligned with the grooves of a lower tier. When the grooves from separate tiers are not aligned, the water may not be able to drain properly. Furthermore, grooved foam presents a potential for residual moisture entrapment where the foam surface touches the wall due to surface tension of the water resting on the surface of the foam causing absorption of water into the foam resulting in elevated moisture levels on the surface of the substrate.
As a result of the issues associated with using foam, weather resistive barriers, also known as house wraps, are currently being used. In fact, recent code changes now require a weather resistant barrier to separate the outer building cladding from the inner sheathing material. Such a weather resistant barrier should be waterproof, but still breathable. One weather resistant material commonly used today is Tyvek®, a registered trademark of the DuPont Company. Tyvek is a synthetic material that lets water vapor escape without allowing liquid water to enter. Although Tyvek is a weather resistant material, it fails to provide separation from the outer building cladding. Corrugated Tyvek has been used to create some separation, however, it fails to provide an adequate drainage mechanism for the trapped moisture to escape because as gravity pulls water down through the Tyvek, capillary action causes the water to get “caught” in locations where the corrugated Tyvek is touching the sheathing material. This prevents much of the water from escaping the inner walls of the building structure.
To provide drainage for the trapped moisture, rainscreen drainage mats have been installed between a weather resistive barrier and the outer building cladding. An example of a rainscreen drainage mat is Enkamat® sold by Colbond Inc. To improve installation time, rainscreen drainage mats have been bonded to an all weather resistive barrier, such as tar paper or Tyvek. Therefore, a single application can be installed on the sheathing material of the building. A facer material, such as a filter fabric, is typically installed on top of the drainage mat before the outer building cladding is installed. However, the installation of the facer material on top of the drainage mat results in a two step process. Not only does the two step process increase installation time, but it also results in the use of more fasteners that may allow water penetration into the wall.
Another concern associated with the current weather resistive barriers and drainage mat combinations is that they do not adequately prevent water from entering interfaces between dissimilar building materials, such as the interface where the window or door meets the outer building cladding. Although flashing is used to resolve this issue, it is often improperly installed resulting in water entering at the interface. In addition, flashing does not provide a seal at the interface that is capable of keeping the water out.
Therefore, there is a need for a drainage system that includes all three layers, a weather resistive barrier, a drainage mat, and a facer material, for a faster and easier single unit installation process. Likewise, there is a need for a breathable water resistant sheathing material and drainage system that can prevent water damage by creating a seal around the interface.